1. Field of the Inventions
The present invention relates in general to noise reduction in articulating connections, and more particularly, to noise reduction in articulating connections in devices for supporting a limb, including orthotic and prosthetic devices.
2. Description of the Related Art
Prosthetic devices, orthotic devices and many other mechanical parts, utilize articulated connections between members requiring motion or movement relative to each other, a user, or the surrounding environment. Common articulating connections often include a bushing, or a bore in the base material, along with a pin that extends through the bushing or bore. Articulating capability of the pin and bushing relative to each other, such as free rotation by and about the pin requires a slight clearance between a pin outer diameter and an inner surface of the bore or bushing.
Cyclical loading of the articulating connection (e.g., back-and-forth in opposing directions) results in an impact between the pin and bushing or bore, where the interacting load bearing contact surfaces of the pin and bushing lose contact with each other for a short while before reestablishing contact. Such an impact during the operation of the articulating connection results in accelerated or undesired wear of the individual interacting members and elements. Additionally, the cyclical contact between the pin and bushing or bore can generate noise during use of the articulating connection (e.g., a clicking noise). In certain device applications, such wear and/or noise is undesirable.
A conventional articulating connection 12 in a prosthetic or orthotic limb support member P is shown in FIGS. 1-3, which depict the disadvantageous features of a conventional articulating connection discussed above. The articulating connection 12 includes a load bearing pin 16, which can be removably attached to, or integral with, the limb support member P, and a bushing 18 into which the load bearing pin 16 extends. The interacting diametral features of the load bearing pin 16 and the bushing 18 are generally sized and toleranced to allow installation and assembly of the pin 16 and the bushing 18 and allow rotational movement between the load bearing pin 16 and the bushing 18.
Generally, the load bearing pin 16 has an outer diameter smaller than an inner diameter of the bushing 18 that defines a clearance E between the two different diameters that is sufficient to allow the pin 16 and the bushing 18 to easily be assembled and to articulate with respect to each other. Creating an articulating connection 12 with a small clearance increases the time and cost of manufacture of the articulating connection 12, as well as presents the likelihood of seizingly coupling the two members together and precluding all movement between the load bearing pin 16 and the bushing 18 (e.g., as the material of the pin 16 and bushing 18 expand due to heat generation during use). Articulating connections with a larger clearance can be manufactured faster and at lower cost. However, the greater the clearance, the greater the cyclical load impact and noise between the load bearing pin 16 and the bushing 18, as discussed above.
Thus, FIG. 1 depicts the typical unloaded and concentrically situated relationship between the load bearing pin 16 and the bushing 18 with a substantially similar clearance gap E all around the diameter of the load bearing pin 16. However, as depicted in FIGS. 2 and 3, during operation of the limb support member P, the coupled members disposed about the articulating connection will impart a first force on the bushing 18 and the load bearing pin 16 such that the load bearing pin is eccentrically disposed to contact the bushing 18 at a common point of surface tangency between the bushing 18 and the load bearing pin 16. Thus a first eccentric clearance E′ is established between the bushing 18 and the load bearing pin 16. Upon further operational use of the prosthetic device a second substantially opposing load is imparted on the articulating connection such that a second eccentric clearance E″ is established between the bushing 18 and the load bearing pin 16, where E″ is substantially diametrally opposed about eccentric clearance E′. A conventional articulating connection, for example in a prosthetic or orthotic device, thus produces cyclical opposing radial impact loads on the load bearing pin 16 and the bushing 18, as well as adjacent articulating connection members of the prostheses or orthoses linkages. The cyclical impact loading impairs the wear life of the articulating connection members and produces undesirable operating noise.
Accordingly, there is a need for an improved articulating connection that solves some of the disadvantages discussed above.